Conventional motor-bearing holding structures that rotatably hold, on the bearing, the rotor of a motor driving an electric control valve include an example in which “The rotor portion of a motor driving the EGR (exhaust gas recirculation) valve of an internal combustion engine is integrally molded with a magnet, a ball bearing, and a resin-made magnet holder supporting these parts by means of insert-molding” (For example, see JP-A-10-082349).
To be more specific, the bearing holding structure is a structure in which part of the magnet holder constituting the rotor protrudes in a sword-guard shape to support the inner ring of the bearing holding the rotor.
However, such a bearing holding structure can have only holding strength obtained with the resin for the bearing holding strength, and is unsatisfactory in terms of reliability and durability. Particularly, in a high-power motor driving an electric control valve, the output power of the motor is transmitted from the output shaft thereof to the bearing inner-ring holding part through the rotor to damage the resin securing the bearing inner-ring, thereby causing the maloperation of the motor.
Patent Reference 1: JP-A-10-082349
In the conventional motor-bearing holding structure, there is a problem that the structure can have only holding-strength obtained with the resin for the bearing holding strength, and the structure, therefore, has low reliability and durability.
The present invention has been accomplished to solve the above-mentioned problem. An object of the present invention is to provide a motor-bearing holding structure with improved reliability and durability.